Cessna 210 pilot reported total loss of electrical power was caused by the failure of the alternator. The flight crew established cell phone communications with ATC and was provided a vector to a suitable airport. The flight crew diverted and made a precautionary landing.

Narrative

I was climbing VMC at night through 6;000 ft. MSL on an IFR flight plan cleared to 9;000 ft.; heading 140; when my lights dimmed and then had a total loss of electrical power in the cockpit. My Garmin G5's and iPad were the only instruments with power. I had no comms or transponder to squawk 7600. I was outside controlled airspace so I turned to return to ZZZ. I had no way of notifying ZZZ approach of my turn or situation. My wife was with me and I provided her a phone number for ZZZ approach from my iPad and we informed them of our situation and they provided a vector to ZZZ. Cell signal was broken and barely readable. Signal cutoff very soon into the phone call. I wanted ZZZ because the winds were gusting to 20 kts. out of 190 and I did not want the added crosswind near my max crosswind component at another airport. I was already facing a dark cockpit; no comms; pumping the landing gear down manually; turbulence; and no flaps. We cleared the area for traffic; pumped the gear down; and landed at ZZZ without incident. Immediately when I landed and cleared the Runway I called ZZZ approach on my phone and informed them of my location and canceled IFR. The lady was glad I made it with no incidence and canceled my flight plan. I did not see any advance warning of this situation happening but I may have noticed a drop in voltage sooner? It seemed to discharge and fail almost immediately and seemed like an alternator failure and sudden discharge. Aircraft was going to maintenance the next day. I will practice this failure in the future to be more prepared. I am also investigating a standby alternator for the aircraft.